JP4965123B2 - Piezoelectric actuator, manufacturing method thereof, and liquid ejection device - Google Patents

Description

  The present invention relates to a piezoelectric actuator, a method for manufacturing the same, and a liquid ejection device. More specifically, the present invention is suitable for, for example, a fuel injection injector, an ink jet printer, and the like. The present invention relates to a piezoelectric actuator that can be suitably used as a liquid ejection device, a manufacturing method thereof, and a liquid ejection device.

Conventionally, products using piezoelectric ceramics include, for example, piezoelectric actuators, filters, piezoelectric resonators (including oscillators), ultrasonic vibrators, ultrasonic motors, piezoelectric sensors, and the like. Among these, the piezoelectric actuator has a very high response speed to electrical signals of ^10-6 seconds, so it can be used for positioning of XY stages in semiconductor manufacturing equipment and print heads (liquid ejection devices) of inkjet printers. Has been. In particular, due to the recent increase in speed and price of color printers, there is an increasing demand for use in piezoelectric actuators for ink ejection such as inkjet printers.

  As such a piezoelectric actuator, for example, in Patent Document 1, a plurality of displacement elements including a piezoelectric ceramic layer (piezoelectric layer) and a pair of electrodes sandwiching the piezoelectric layer are provided on the surface of a ceramic substrate. A piezoelectric actuator is described.

  FIG. 4 is a schematic cross-sectional view showing a conventional piezoelectric actuator as described in Patent Document 1. As shown in FIG. As shown in the figure, the piezoelectric actuator 61 includes a piezoelectric layer 65 and a pair of electrodes (an internal electrode 64 and a surface electrode 66) sandwiching the piezoelectric layer 65 on the surface of the piezoelectric diaphragm 62. A plurality of displacement elements 67 are provided. When a driving voltage is applied between the surface electrode 66 and the internal electrode 64, the displacement element 67 is displaced.

Here, the internal electrode 64 generally contains silver, and the piezoelectric actuator 61 is obtained by firing.
However, at the time of firing, there is a problem that silver contained in the internal electrode 64 diffuses into the piezoelectric layer 65 and the piezoelectric characteristics deteriorate. There is also a problem that silver is precipitated at the grain boundaries of the crystal phase constituting the piezoelectric layer 65. When silver precipitates at the grain boundary, silver migration (silver migration) occurs depending on the use environment (applied voltage, humidity, etc.), and the insulation resistance of the piezoelectric layer 65 decreases, resulting in a decrease in piezoelectric characteristics. End up. These problems are conspicuously generated in a piezoelectric actuator having a thickness of 100 μm or less in which silver easily diffuses.

  In Patent Document 2, a conductive pace containing silver is used to form an internal electrode, the laminated body constituting the piezoelectric actuator is fired, the oxygen concentration in the heating process and the holding process is 21% by volume or more, and the cooling process Describes a method for producing a laminated piezoelectric ceramic element (piezoelectric actuator) performed in an atmosphere in which the oxygen concentration of this is 0.05 to 3% by volume. According to this document, silver dissolved in the ceramic grains (crystalline phase of the internal electrode) during the temperature rising process and holding process is precipitated at the grain boundary during the temperature lowering process, which improves the piezoelectric characteristics and reliability. ing.

  However, depending on the use environment, silver migration due to silver precipitated at the grain boundaries occurs and the insulation resistance decreases, that is, the piezoelectric actuator obtained by the manufacturing method described in Patent Document 2 may have low environmental reliability.

On the other hand, lead zirconate titanate (PZT) is used as a piezoelectric layer of a piezoelectric actuator, but Non-Patent Document 1 describes a silver diffusion investigation into a specific PZT.
However, in the PZT described in this document, silver diffuses to a depth of 200 μm at 650 ° C. in 1 hour. For this reason, when this PZT is used as a piezoelectric layer of a piezoelectric actuator having a thickness of 100 μm or less, there is a problem that silver diffuses throughout the piezoelectric layer and the piezoelectric characteristics of the piezoelectric actuator deteriorate.
JP 2004-165650 A JP 2003-192436 A JOURNAL OF MATERIALS SICEENCE 28 (1993) p. 5189-5192

  An object of the present invention is to provide a piezoelectric actuator that exhibits stable piezoelectric characteristics and excellent environmental reliability, a method for manufacturing the same, and a liquid ejection device.

  As a result of intensive studies to solve the above problems, the inventor of the present invention has a piezoelectric actuator in which the internal electrode contains silver and lead, and the piezoelectric layer contains a perovskite crystal phase containing lead as a main crystal phase. In this case, since the diffusion of silver from the internal electrode to the piezoelectric layer can be suppressed, stable piezoelectric characteristics can be obtained, and the precipitation of silver at the grain boundary of the piezoelectric layer can also be suppressed. The inventors have found a new finding that the piezoelectric actuator is excellent in performance, and have completed the present invention.

That is, the piezoelectric actuator of the present invention has the following configuration.
(1) internal electrode and the piezoelectric layer on the surface of the piezoelectric vibrating plate made of piezoelectric ceramics are laminated in this order, be further arranged a plurality of surface electrodes on the piezoelectric layer, the displacement for each said surface electrode element is configured, a thickness of 100μm or less of the piezoelectric actuator so as to displace the displacement element by applying each independently driving voltage of the surface electrode, the internal electrodes, the lead The piezoelectric layer is fired including silver particles provided with a coating layer containing, and the piezoelectric layer contains 0.4% by weight or less of silver and a perovskite crystal phase containing lead as a main crystal phase. A piezoelectric actuator characterized by containing silver and substantially no silver deposition at the grain boundaries of the main crystal phase.
(2) the said internal electrodes, which further contains palladium (1) Symbol mounting of the piezoelectric actuator.
(3 ) The main crystal phase is a lead zirconate titanate-based perovskite crystal phase, the content of the A site composed of lead in the perovskite crystal phase and a substitution element of the lead, and substitution between titanium and the titanium The piezoelectric actuator according to (1) or (2) , wherein the molar ratio A / B with respect to the content of the B site made of an element is 0.98 or more and less than 1.

The manufacturing method of the piezoelectric actuator of the present invention has the following configuration.
( 4 ) A first step of producing a ceramic green sheet, a second step of printing an internal electrode paste on the surface of at least one ceramic green sheet produced in the first step, and the first step A third step of laminating the ceramic green sheets produced in the step and the second step to produce a laminated body, a fourth step of firing the laminated body to obtain a laminated sintered body, and the laminated firing. A piezoelectric actuator manufacturing method including a fifth step of forming a surface electrode pattern on the surface of the bonded body, wherein the internal electrode paste in the second step is provided with a coating layer containing lead on the surface of silver particles A method for producing a piezoelectric actuator, comprising a conductive material powder obtained.
( 5 ) The method for producing a piezoelectric actuator according to ( 4 ), wherein the conductor raw material powder further includes a palladium layer provided between the silver particles and the coating layer.
( 6 ) The method for manufacturing a piezoelectric actuator according to ( 4 ) or ( 5 ), wherein in the fourth step, the oxygen concentration of the firing atmosphere when firing the laminate is 21% by volume or more.
( 7 ) The method for manufacturing a piezoelectric actuator according to any one of ( 4 ) to ( 6 ), wherein the coating layer is composed of lead particles having an average particle diameter of 0.1 μm or less.

Liquid discharge apparatus of the present invention, the (1) to (3) a piezoelectric actuator according to any of, on the flow path member in which a plurality of liquid flow paths are arranged with a liquid discharge hole, the liquid flow path wherein the mounted by aligning the position of the surface electrode and the.

  According to the present invention, the internal electrode contains silver (Ag) and lead (Pb), and the piezoelectric layer contains a perovskite type crystal phase containing Pb as the main crystal phase. The diffusion of Ag to the body layer is suppressed, the amount of Ag diffusion to the piezoelectric layer is reduced, and as a result, stable piezoelectric characteristics can be obtained. Moreover, since precipitation of Ag at the grain boundaries of the crystal phase is suppressed, a decrease in insulation resistance of the piezoelectric layer due to silver migration is suppressed, and a piezoelectric actuator having excellent environmental reliability can be obtained.

<Piezoelectric actuator>
Hereinafter, an embodiment of a piezoelectric actuator of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the piezoelectric actuator of the present embodiment. FIG. 2 is an enlarged schematic explanatory view showing the piezoelectric layer according to the present embodiment.

  As shown in FIG. 1, the piezoelectric actuator 1 includes a piezoelectric diaphragm 2, an internal electrode 3, a piezoelectric layer 4, and a surface electrode 5. The body layer 4 and the surface electrode 5 are laminated in this order. Further, the piezoelectric diaphragm 2 and the piezoelectric layer 4 are composed of sheet-like members, and are formed in substantially the same shape and size in plan view.

  The internal electrode 3 and the surface electrode 5 constitute an electrode of the piezoelectric actuator 1, and a plurality of the surface electrodes 5 are formed on the surface of the piezoelectric layer 4. As a result, a plurality of displacement elements 6 configured by sandwiching the piezoelectric layer 4 between the internal electrode 3 and the surface electrode 5 are arranged on the surface of the piezoelectric diaphragm 2.

  The polarization method required for the displacement of the piezoelectric actuator 1 (displacement element 6) is not particularly limited, and may be polarized according to the required displacement form. In particular, the piezoelectric actuator 1 is a unimorph type described later. In order to obtain an actuator, it is preferable that at least a portion of the piezoelectric layer 4 sandwiched between the internal electrode 3 and the surface electrode 5 is polarized in the stacking direction.

  When an external wiring board is connected to the surface electrode 5 and a voltage is applied between the electrodes (surface electrode 5 and common electrode 3), the portion sandwiched between the surface electrode 5 and the internal electrode 3 to which the voltage is applied The piezoelectric layer 4 is displaced. Specifically, when a driving electrode is applied to the surface electrode 5, the displacement in the plane direction (direction orthogonal to the stacking direction) is suppressed by the piezoelectric diaphragm 2, so that the displacement element 6 bends in the stacking direction. That is, the piezoelectric actuator 1 operates as a unimorph type actuator.

  The thickness of the piezoelectric actuator 1 as described above is 100 μm or less, preferably 80 μm or less, more preferably 65 μm or less, and further preferably 50 μm or less. Thereby, since a large displacement can be obtained, it is possible to realize high-efficiency driving at a low voltage. The lower limit of the thickness of the piezoelectric actuator 1 has sufficient mechanical strength and is 3 μm, preferably 5 μm, more preferably 10 μm, and further preferably 20 μm in order to prevent breakage during handling and operation. It is good.

  Here, as described above, when the thickness of the piezoelectric actuator is 100 μm or less, deterioration of piezoelectric characteristics due to diffusion of Ag contained in the internal electrode to the piezoelectric layer during firing, and the piezoelectric layer Although the insulation resistance of the piezoelectric layer is likely to decrease due to the precipitation of Ag at the grain boundaries of the constituent crystal phases, the piezoelectric actuator 1 can suppress the diffusion of Ag and the precipitation of Ag.

  Specifically, the internal electrode 3 of the piezoelectric actuator 1 contains Ag and Pb, and the piezoelectric layer 4 contains a perovskite crystal phase containing Pb as the main crystal phase. When the internal electrode 3 and the piezoelectric layer 4 are configured in this way, the diffusion of Ag from the internal electrode 3 to the piezoelectric layer 4 is suppressed during firing, and Ag precipitates at the grain boundaries of the main crystal phase. Is suppressed.

  The reason why the diffusion of Ag is suppressed is presumed as follows. That is, in the present invention, as will be described later, as the internal electrode paste used when forming the internal electrode 3, a paste containing a conductor raw material powder in which a coating layer containing Pb is provided on the surface of Ag particles is used. Thus, when the Ag particle surface is coated with Pb, the mutual diffusion of Pb and Ag is performed on the Ag particle surface, and as a result, it is presumed that the diffusion of Ag is suppressed.

  Further, the reason why the precipitation of Ag is suppressed is presumed as follows. That is, since the diffusion of Ag is suppressed for the reason described above, first, the amount of Ag diffused from the internal electrode 3 to the piezoelectric layer 4 is reduced. Further, Ag diffused in the piezoelectric layer 4 is dissolved in the main crystal phase 4a of the piezoelectric layer 4 as shown in FIG. 2, and as a result, it is suppressed that Ag precipitates at the grain boundaries 4b. It is inferred that

  Furthermore, in the present invention, the proportion of Ag contained in the piezoelectric layer 4 is 0.4% by weight or less with respect to the total weight of the piezoelectric layer 4, and the grain boundaries 4b of the main crystal phase 4a of the piezoelectric layer 4 are present. Substantially no precipitation of Ag. Thereby, a decrease in insulation resistance of the piezoelectric layer 4 due to silver migration is suppressed, and the piezoelectric actuator 1 having excellent environmental reliability is obtained. On the other hand, when the proportion of Ag exceeds 0.4% by weight, Ag may be precipitated at the grain boundaries 4b.

  Confirmation that the internal electrode 3 contains Ag and Pb and that the precipitation of Ag is not substantially observed at the grain boundaries 4b of the main crystal phase 4a can be confirmed using, for example, a transmission electron microscope (TEM). The presence or absence can be confirmed by enlarging the magnification to about 100,000 times and conducting elemental analysis with EDS. The amount of Ag contained in the piezoelectric layer 4 may be determined by, for example, mirror-polishing the cross section of the piezoelectric layer 4 and performing quantitative analysis in an area of 10 μm × 10 μm by WDS / EPMA.

(Piezoelectric layer)
As the piezoelectric layer 4, ceramics (piezoelectric ceramics) exhibiting piezoelectricity can be used, and as described above, a perovskite type crystal phase containing Pb is contained as a main crystal phase. Examples of the compound constituting the main crystal phase include lead magnesium niobate (PMN type), lead nickel niobate (PNN type), lead zirconate titanate (PZT) containing Pb, lead titanate and the like. Substances are preferred. In particular, a crystal containing Pb as the A site constituent element and zirconium (Zr) and titanium (Ti) as the B site constituent element is preferable. With such a composition, a piezoelectric layer having a high piezoelectric constant can be obtained. Among these, lead zirconate titanate (PZT) and lead titanate are suitable for adding a large displacement. An example of a perovskite crystal is PbZrTiO ₃ .

  In particular, in the present invention, the main crystal phase is a lead zirconate titanate-based perovskite crystal phase, the content of A site consisting of Pb of the perovskite crystal phase and a substitution element of Pb, Ti, It is preferable that the molar ratio A / B with respect to the content of the B site composed of the Ti substitution element is 0.98 or more and less than 1. This reduces the stoichiometry of the A site relative to the stoichiometry of the B site, so that Ag is dissolved in the main crystal phase 4a of the piezoelectric layer 4 without leaving Ag at the grain boundaries 4b of the piezoelectric ceramic. be able to.

  In addition to the compounds constituting the main crystal phase, other compounds may be used in combination. Examples of other compounds include Bi layered compounds (layered perovskite type compounds), tungsten bronze type compounds, Nb perovskite type compounds [Nb acid alkali compounds (NAC) such as sodium Nb acid, and Nb acid alkalis such as barium Nb acid. An example is an earth compound (NAEC)].

Furthermore, other oxides may be mixed with the piezoelectric ceramic, and other elements may be substituted at the A site and / or the B site as subcomponents as long as the properties are not adversely affected. For example, it may be a solid solution of Pb (Zn _1/3 Sb _2/3 ) O ₃ and Pb (Ni _1/2 Te _1/2 ) O ₃ to which Zn, Sb, Ni and Te are added as subcomponents.

  The thickness of the piezoelectric layer 4 is about 5 to 50 μm, preferably about 10 to 30 μm. Thereby, the displacement element 6 can show a high displacement. On the other hand, when the thickness is less than 5 μm, the mechanical strength is lowered, and there is a risk of breaking during handling and operation. When the thickness is more than 50 μm, the displacement may be lowered, which is not preferable.

  In particular, in the present invention, the thickness of the piezoelectric layer 4 is preferably 20 μm, and the leakage current value when a voltage of 20 V is applied to the piezoelectric layer 4 is preferably 150 pA or less. Since the piezoelectric layer 4 has such a low leakage current value, that is, a high insulation resistance, excellent piezoelectric characteristics can be exhibited. In the present invention, as described above, Ag precipitation is suppressed at the grain boundaries 4b of the main crystal phase 4a, so that the piezoelectric layer 4 can maintain a high insulation resistance for a long time.

  The leakage current value is a value obtained by measuring with a current measuring device. Examples of the device include an electrometer 6517A manufactured by KEITHLEY. Specifically, first, of the two terminals of the measuring apparatus, one of the terminals is brought into contact with the surface electrode 5 and the other terminal is brought into contact with the side surface of the internal electrode 3. A voltage of 20V is applied to the terminal, and the leakage current value can be measured from the potential difference between both terminals.

(Piezoelectric diaphragm)
The piezoelectric diaphragm 2 is made of piezoelectric ceramics and is preferably made of substantially the same material as the piezoelectric layer 4 described above. As a result, when the piezoelectric diaphragm 2 and the piezoelectric layer 4 are fired at the same time, firing shrinkage in the piezoelectric actuator 1 can be made uniform, and warping deformation can be suppressed. In addition, when the piezoelectric actuator 1 is applied to a liquid discharge apparatus such as an ink jet recording head, it is preferable that the material has excellent ink resistance such as corrosion resistance and water resistance against ink used.

  The thickness of the piezoelectric diaphragm 2 is about 5 to 50 μm, preferably about 10 to 30 μm. Thereby, the piezoelectric actuator 1 can be made into a unimorph type.

(Internal electrode)
The internal electrode 3 contains Ag and Pb as described above. The proportion of Ag and Pb is such that the Pb content is 0.1 to 5% by weight, preferably 0.1 to 0.5% by weight, based on the total amount of Ag. On the other hand, if the Pb content is lower than 0.1% by weight, the Ag diffusion and Ag precipitation may not be suppressed. If the Pb content exceeds 5% by weight, Pb is included more than necessary. This is not preferable.

  In addition to Ag and Pb, another metal having conductivity may be used in combination. Examples of other metals include gold (Au), palladium (Pd), platinum (Pt), copper (Cu), aluminum (Al), and alloys thereof. Examples of the alloys include Ag-Pd. An alloy is mentioned. In particular, in the present invention, it is preferable that the internal electrode 3 further contains Pd in order to more effectively suppress the diffusion of Ag.

  The average particle diameter of Ag is, for example, 0.1 to 5 μm, preferably 0.1 to 0.5 μm. The average particle diameter of Pb is, for example, 0.01 to 5 μm, preferably 0. It is good that it is 0.01-0.3 micrometer. The average particle diameter of the other metal is not particularly limited, but is, for example, 0.1 to 5 μm, preferably 0.1 to 0.5 μm. The average particle diameter is a value obtained by measuring with a particle size distribution measuring apparatus.

  The thickness of the internal electrode 3 needs to be conductive and not to prevent displacement, and is usually about 0.5 to 5 μm, preferably 0.5 to 3 μm. In particular, in the present invention, it is preferable that the average thickness of the internal electrode 3 is 1 μm or less, and the maximum diameter of Ag particles contained in the internal electrode 3 is 5 μm or less. Thereby, since the maximum particle diameter of Ag used for the internal electrode 3 is larger than the average thickness of the internal electrode 3, the electrode has a particle shape with a large aspect ratio. As a result, the internal electrode 3, the piezoelectric layer 4 and the piezoelectric layer are formed. Adhesiveness with the diaphragm 2 can be improved, and these can be prevented from peeling off.

(Surface electrode)
The surface electrode 5 is not particularly limited as long as it has conductivity. For example, Au, Ag, Pd, Pt, Cu, Al, or an alloy thereof can be used. The average particle diameter of these metals is not particularly limited and is, for example, 0.1 to 5 μm, preferably 0.1 to 0.5 μm. This average particle diameter is a value obtained by measuring in the same manner as the internal electrode.

  Moreover, the thickness of the surface electrode 5 needs to be a grade which has electroconductivity and does not prevent a displacement, for example, about 0.1-2 micrometers, Preferably it is 0.1-0.5 micrometer, More preferably, it is 0.00. It should be 1 to 0.3 μm.

<Manufacturing method>
Next, a method for manufacturing the piezoelectric actuator 1 described above will be described.
(First step)
First, a piezoelectric ceramic raw material powder as a raw material for the piezoelectric layer 4 and the piezoelectric diaphragm 2 is prepared. At this time, as the piezoelectric ceramic raw material powder used as the raw material of the piezoelectric layer 4, a piezoelectric ceramic raw material powder that contains a perovskite crystal phase containing Pb as a main crystal phase by firing is prepared.

  The average particle size of the piezoelectric ceramic raw material powder is preferably 1 μm or less, particularly 0.7 μm or less, and more preferably 0.6 μm or less. By setting the average particle size of the piezoelectric ceramic raw material powder to 1 μm or less, uniform firing shrinkage can be obtained during sintering, and the homogeneous piezoelectric layer 4 and the piezoelectric diaphragm 2 can be obtained. The piezoelectric ceramic raw material powder and the organic binder component are mixed to prepare a sheet forming slurry. Next, a required number of ceramic green sheets are produced by using this forming slurry by a general sheet forming method such as a roll coater method, a slit coater method, or a doctor blade method.

  The ceramic green sheet obtained above is pressurized as necessary. By pressurizing the ceramic green sheet after forming the sheet, it is possible to increase the density of the sheet and reduce height variation and density variation. As a pressurizing method, a known method can be adopted, but it is preferable to use a roll pressurizing method, a plane pressurizing method, a hydrostatic pressurizing method or the like from the viewpoint that a uniform height can be easily obtained. Moreover, although the pressure at the time of pressurization changes with material composition, the amount of organic binders, the height of a green sheet, etc., it is good to pressurize with the pressure of 10-100 MPa normally, Preferably it is 20-50 MPa, More preferably, it is 30-40 MPa. . When the height variation of each green sheet obtained by pressing is 15% or less, particularly 10% or less, the height variation of the piezoelectric layer 4 and the diaphragm 2 formed after firing is reduced, and warp deformation is caused. Can be prevented.

(Second step)
Next, an internal electrode paste containing the electrode material (Ag or the like) exemplified for the internal electrode 4 is prepared. In the present invention, the internal electrode paste includes a conductor raw material powder in which a coating layer containing Pb is provided on the surface of Ag particles. Thus, since the Ag particle surface is coated with Pb, as described above, the mutual diffusion of Pb and Ag is performed on the Ag particle surface. As a result, the diffusion of Ag is suppressed and the precipitation of Ag is also suppressed. It is guessed.

  The coating layer is preferably composed of Pb particles having an average particle size of 0.1 μm or less. By using such fine particles, diffusion of Ag during sintering can be more effectively suppressed.

  Moreover, it is preferable that the conductor raw material powder further includes a Pd layer between the Ag particles and the coating layer. Thereby, the reaction layer of Pb and Pd can be effectively formed on the surface of the Ag particles, and the diffusion of Ag into the piezoelectric layer 4 can be effectively suppressed. As a result, the piezoelectric layer being sintered Ag diffusion to 4 is suppressed.

  Although it does not specifically limit as a preparation method of the above conductor raw material powders, For example, it can prepare as follows. That is, first, Ag particles and Pb particles having a predetermined average particle diameter, and further Pd particles as necessary are prepared. Subsequently, the conductor raw material powder in which the coating layer containing Pb is provided on the surface of the Ag particles can be obtained by mixing the Ag particles and the Pb particles by coating the surface of the Ag particles with Pb particles. . At this time, the Pb particles are preferably in the form of PbO.

  When the Pd layer is provided, first, the Pd particle is coated on the surface of the Ag particle by coating the Pd particle, and the Pd layer is provided by mixing the Ag particle and the Pd particle, and then the Pb layer is formed on the surface of the Pd layer. A conductor raw material powder in which a Pd layer is further provided between the Ag particles and the coating layer is obtained by mixing Ag particles and Pb particles formed with a Pd layer by coating with particles. Can do.

  The internal electrode paste contains components such as an organic vehicle such as ethyl cellulose in addition to the electrode material. Then, the internal electrode paste is printed on the surface of the ceramic green sheet produced as described above by a method such as screen printing. In this case, the thickness is desirably adjusted to 1 to 3 μm, and the variation (difference between the maximum value and the minimum value) is set to 0.5 to 1 μm. Further, if necessary, a via hole may be formed in a part of the green sheet, and a via conductor may be inserted therein.

(Third step)
The ceramic green sheets produced in the first step and the second step are laminated and brought into close contact to produce a laminate. In addition, as a method of close contact, a method of using a close contact liquid containing an adhesive component, a method of closely attaching an organic binder component in a green sheet by heating, a close contact method only by pressure, etc. Can be illustrated.

(Fourth process)
The laminated body obtained in the third step is degreased as necessary to remove organic components in the laminated body, and then fired at 900 to 1200 ° C. in a (high concentration) oxygen atmosphere. A laminated sintered body is obtained. At this time, Ag contained in the internal electrode paste is suppressed from diffusing into the ceramic green sheet to be the piezoelectric layer 4, and Ag is present at the grain boundaries 4 b of the main crystal phase 4 a constituting the piezoelectric layer 4. Precipitation is suppressed.

  Here, the oxygen concentration of the firing atmosphere when firing the laminate is 21% by volume or more, preferably 80% by volume or more. As a result, the diffused Ag is more effectively dissolved in the main crystal phase 4 a of the piezoelectric layer 4. The most preferred oxygen concentration is 100% by volume.

  In the fourth step (firing step), the laminated body obtained in the third step is stacked in multiple stages via a sample base plate made of zirconia or magnesia, and further, It is desirable to sinter with a weight. By adopting such a method, warping deformation of the laminated sintered body is suppressed, and a piezoelectric actuator made of a thin sintered body having a thickness of 100 μm or less can be provided.

(Fifth step)
Next, a surface electrode paste containing the electrode material exemplified for the surface electrode 5 is prepared, and the surface electrode pattern is screen printed on the surface of the laminated sintered body obtained in the fourth step using the paste. Print by the method. And the surface electrode 5 is formed by performing a baking process at 500-800 degreeC, Preferably 650-800 degreeC. And the piezoelectric actuator 1 which is a laminated piezoelectric material is obtained by polarizing the piezoelectric material layer 4.

<Liquid ejection device>
As described above, the piezoelectric actuator of the present invention includes a plurality of displacement elements on one substrate (piezoelectric vibration plate), and thus can be suitably used for a liquid ejection apparatus such as an ink jet recording head. Hereinafter, an embodiment of a liquid ejection apparatus including the piezoelectric actuator of the present invention will be described. FIG. 3 is a schematic cross-sectional view showing the liquid ejection apparatus of the present embodiment. In FIG. 3, the same or equivalent parts as those in FIGS. 1 and 2 described above are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 3, the liquid ejection device 20 includes a plurality of liquid flow paths 16a having liquid ejection holes 18 arranged in parallel, and a flow path member 16 on which a partition wall 16b is formed as a wall that partitions the liquid flow paths 16a. The piezoelectric actuator 1 described above is joined to the above. The piezoelectric diaphragm 2 constitutes a part of the wall of each liquid channel 16a.

  A common liquid supply flow path (not shown) provided in the flow path member 16 is connected to the liquid flow path 16a configured as described above, and liquid from the outside is supplied from the liquid supply flow path. Each liquid channel 16a is supplied and filled. When the liquid is discharged, the discharged amount of liquid is configured to flow into each flow path 16a via the supply flow path.

  The channel member 16 is obtained by a rolling method or the like, and the liquid discharge hole 18 and the liquid channel 16a are provided by being processed into a predetermined shape by etching or the like. The flow path member 16 is preferably formed of at least one selected from the group consisting of Fe—Cr, Fe—Ni, and WC—TiC, and is made of a material particularly excellent in corrosion resistance to ink. Desirably, the Fe-Cr system is more preferable.

  The flow path member 16 and the piezoelectric actuator 1 are preferably bonded together through an adhesive layer, for example, so that the piezoelectric diaphragm 2 is in contact with the space of the liquid flow path 16a. 6 are joined so that each surface electrode 5 and each liquid flow path 16a correspond.

  As the adhesive layer, various known ones can be employed, and epoxy resin or phenol having a thermosetting temperature of 100 to 150 ° C. without affecting the piezoelectric actuator 1 or the flow path member 16 by heat. It is preferable to use at least one thermosetting resin adhesive selected from the group of resins and polyphenylene ether resins. By heating to the thermosetting temperature using such an adhesive layer, the piezoelectric actuator 1 and the flow path member 16 can be heat-bonded, and the liquid ejection device 20 can be obtained.

  Then, by applying a driving voltage to the predetermined surface electrode 5 among the plurality of surface electrodes 5 in the piezoelectric actuator 1 and displacing the predetermined displacement element 6, the volume of the liquid channel 16 a is changed, and the liquid channel The liquid flowing through 16 a can be discharged from the liquid discharge hole 18.

  In addition, the liquid ejection device 20 having the above-described configuration can eject at high speed and high accuracy, and can be suitably applied as an inkjet recording head (printing head). That is, the liquid is ink, the ink is ejected from the liquid ejection hole 18, and characters or pictures are displayed on the surface of a display member (not shown) arranged to face the liquid ejection hole 18. Is preferred.

  As mentioned above, although one Embodiment of this invention was shown, it cannot be overemphasized that this invention can be applied not only to the embodiment mentioned above but what was changed and improved in the range which does not deviate from the summary of this invention. For example, in the above-described embodiment, the case where each of the piezoelectric diaphragm 2 and the piezoelectric layer 4 is composed of one layer has been described, but the present invention is not limited to this, and the piezoelectric diaphragm and / Or the piezoelectric layer may be composed of a plurality of layers. In this case, the thickness of the piezoelectric actuator can be easily adjusted.

  Further, as described above, the piezoelectric diaphragm 2 is preferably made of substantially the same material as the piezoelectric layer 4, but the compositions of the piezoelectric diaphragm 2 and the piezoelectric layer 4 do not have to be completely identical. The composition may be different as long as the effect of the present invention, that is, a piezoelectric actuator exhibiting stable piezoelectric characteristics and excellent environmental reliability can be obtained.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to a following example.
[Example]
<Manufacture of piezoelectric actuator>
Lead zirconate titanate having a molar ratio A / B shown in Table 1 was prepared as a piezoelectric ceramic raw material powder used for the piezoelectric ceramic layer (piezoelectric diaphragm and piezoelectric layer). Next, a slurry was prepared using this raw material powder, and a plurality of ceramic green sheets were produced by a roll coater method.

  A through hole having a diameter of 100 μm was formed in each green sheet obtained above by die punching. Thereafter, an internal electrode paste containing an Ag—Pd alloy as an electrode material is prepared, and the internal electrode pattern is represented by a screen printing method so that the internal electrode is formed at a desired portion of each green sheet. The thickness shown in FIG.

  Here, the Ag—Pd alloy used for the internal electrode paste was obtained by coating the surface of the alloy with PbO in various addition amounts shown in Table 1. Further, among Ag—Pd alloys, Ag having an average particle diameter shown in Table 1 was used. Further, an electrode material similar to the internal electrode layer was filled in the through-hole, and an electrode material added with 30% by volume of piezoelectric powder as a filler was screen-printed to form a via electrode. The coating was performed by mixing an Ag—Pd alloy and PbO.

  And each green sheet was laminated | stacked and the laminated molded object (laminated body) provided with the internal electrode and the via electrode was produced. Thereafter, this laminate was fired at a temperature of 1000 ° C. in a firing atmosphere of each oxygen concentration shown in Table 1, and then the surface electrode paste of the main component Au was applied to the surface so as to face the internal electrode of the portion constituting the displacement element. Screen printing was performed so that electrodes were formed, and surface electrodes were baked at a temperature of 800 ° C. to obtain each piezoelectric actuator (Sample Nos. 1 to 22 in Table 1). The thickness of each obtained piezoelectric actuator is shown in Table 1 as “laminate thickness”. The thickness of the piezoelectric layer of each piezoelectric actuator was 20 μm or less.

  Note that the internal electrode of each piezoelectric actuator contains Ag and the piezoelectric layer contains a perovskite type crystal phase containing Pb as a main crystal phase. This was confirmed by elemental analysis with EDS.

Each actuator is mounted on a support substrate having a groove shape (opening area 0.16 mm ² ) having a groove width of 0.4 mm and a groove length of 0.4 mm, and having a groove pitch of 0.6 mm and arranged in a matrix in a lattice pattern. Were bonded so that each displacement element was positioned in the opening, and then a voltage was applied to each surface electrode to perform polarization treatment.

<Evaluation of piezoelectric actuator>
The amount of Ag in the piezoelectric layer was evaluated by mirror-polishing the cross section of the piezoelectric layer and performing quantitative analysis in an area of 10 μm × 10 μm with WDS / EPMA.
Precipitation phase evaluation of the grain boundary part was enlarged by a magnification of 100,000 using TEM, and elemental analysis of the grain boundary part was conducted by EDS to confirm the presence or absence.
The leakage current value of the piezoelectric layer was measured with an electrometer 6517A manufactured by KEITHLEY Co., Ltd., after 20 V was applied to the laminate active layer for 1 minute.
These measurement results are shown in Table 1.

  As is clear from Table 1, the sample No. 1 in which the internal electrode contains Pb. 1 to 6, 8 to 15, and 17 to 21 show that there is no precipitation of Ag at the grain boundary, the Ag amount in the piezoelectric layer is 0.4% by weight or less, and the leakage current value is small. Further, as a result of evaluating the Pb amount of the internal electrode of these samples in the same manner as the quantitative analysis of the Ag amount in the piezoelectric layer, Pb having almost the same amount as Pb added when the internal electrode paste was prepared. The amount was contained.

  On the other hand, Sample No. with a piezoelectric actuator thickness greater than 100 μm. No. 16 shows that although Ag is not precipitated at the grain boundary, the displacement amount was determined as a result of evaluating the displacement characteristics. The inferior result was shown with respect to 1-6,8-15,17-21. In addition, the sample No. in which the internal electrode does not contain Pb. In Nos. 7 and 22, Ag precipitated at the grain boundaries. In particular, sample no. No. 7 has a high leakage current value. No. 22 showed a high Ag content in the piezoelectric layer.

It is a schematic sectional drawing which shows the piezoelectric actuator concerning one Embodiment of this invention. It is an expansion schematic explanatory drawing which shows the piezoelectric material layer concerning one Embodiment of this invention. It is a schematic sectional drawing which shows the liquid discharge apparatus concerning one Embodiment of this invention. It is a schematic sectional drawing which shows the conventional piezoelectric actuator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric actuator 2 Piezoelectric diaphragm 3 Internal electrode 4 Piezoelectric layer 4a Main crystal phase 4b Grain boundary 5 Surface electrode 6 Displacement element 16 Flow path member 16a Liquid flow path 16b Partition 18 Liquid discharge hole 20 Liquid discharge apparatus

Claims (8)

Internal electrode and the piezoelectric layer are laminated in this order on the surface of the piezoelectric vibrating plate made of a piezoelectric ceramic, be further arranged a plurality of surface electrodes on the piezoelectric layer, the displacement element is configured for each said surface electrode are, a thickness of 100μm or less of the piezoelectric actuator so as to displace the displacement element by applying each independently driving voltage of the surface electrode,
The internal electrode is fired including silver particles provided with a coating layer containing lead,
The piezoelectric layer contains 0.4% by weight or less of silver, contains a perovskite-type crystal phase containing lead as a main crystal phase, and silver is substantially precipitated at grain boundaries of the main crystal phase. Piezoelectric actuator characterized in that it is not seen. The piezoelectric actuator according to claim 1 , wherein the internal electrode further contains palladium. The main crystal phase is a lead zirconate titanate-based perovskite crystal phase, and is composed of lead in the perovskite crystal phase and an A site content of the lead substitution element, and titanium and the titanium substitution element. 3. The piezoelectric actuator according to claim 1, wherein a molar ratio A / B to the content of the B site is 0.98 or more and less than 1. 4. A first step of producing a ceramic green sheet;
A second step of printing an internal electrode paste on the surface of at least one ceramic green sheet produced in the first step;
A third step of producing a laminate by laminating the ceramic green sheets produced in the first step and the second step;
A fourth step of firing the laminated body to obtain a laminated sintered body;
A method of manufacturing a piezoelectric actuator comprising a fifth step of forming a surface electrode pattern on the surface of the laminated sintered body,
The internal electrode paste in the second step includes a conductor raw material powder in which a coating layer containing lead is provided on the surface of silver particles. The method of manufacturing a piezoelectric actuator according to claim 4 , wherein the conductor raw material powder further includes a palladium layer between the silver particles and the coating layer. The method for manufacturing a piezoelectric actuator according to claim 4 or 5 , wherein, in the fourth step, the oxygen concentration in the firing atmosphere when firing the laminate is 21% by volume or more. The method for manufacturing a piezoelectric actuator according to claim 4 , wherein the coating layer is composed of lead particles having an average particle diameter of 0.1 μm or less. Mounting according piezoelectric actuator according to any of claim 1 to 3, on a flow path member having a plurality of liquid flow paths are arranged with a liquid discharge hole, align the positions of the surface electrode and the liquid flow path A liquid discharge apparatus characterized by being provided with

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